Ultima Thule, the farthest astronomical object to be explored by a human-made probe. It will arrive in New Year 2019

NASA's New Horizons spacecraft captured the world's attention when it buzzed Pluto in July 2015. In January 2019, it will set another record when it reaches another object in the outer edges of the solar system. Known as 2014 MU69 or by its nickname Ultima Thule, the ancient object will provide insight into the early life of the sun and its planets. Unlike other things explored by spacecraft, the tiny chip of ice and rock will be the first to be explored by a spacecraft launched before its discovery.

Both Pluto and 2014 MU69 lie within the Kuiper Belt, a collection of icy rocks that surrounds the outer reaches of the solar system. These objects are thought to be pristine samples from the early solar system, cast out into the boundary zone through gravitational interactions with the larger objects that would grow into planets. Examining them should reveal insight into what was happening in the solar system in the first stages of its lifetime.

NASA announced on Aug. 28, 2015, that it had selected 2014 MU69 as its first choice for the probe's secondary mission.

In 2011, mission scientists used ground-based telescopes to begin searching for a second target, but none of the new discoveries lay within the reach of New Horizons. In 2014, the Hubble Space Telescope joined the search, locating five potential objects. One of them was 2014 MU69, which was labeled 1110113Y after its June 26, 201f4 discovery and PT1 ("potential target 1") after its elevation to one of two possible destinations. In August 2015, the mission team selected 2014 MU69 as its next potential target.

"2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by," New Horizons principal investigator Alan Stern, of the Southwest Research Institute (SwRI) in Boulder, Colorado, said in a statement. "Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen."

New Horizons' final target lies about 1 billion miles (1.6 billion kilometers) beyond Pluto.

In 2017, the New Horizons team requested suggestions for nicknames from the public as part of an outreach campaign. The final decision, Ultima Thule, is a term used in medieval times to mean "beyond the known world." The nickname was submitted by about 40 different people, NASA officials said.

"MU69 is humanity's nex  t Ultima Thule," Stern said.

Far out

Even with Hubble, details of Ultima Thule are difficult to make out. The tiny object is estimated to be just under 30 miles (about 45 km) across, less than 1 percent the size of Pluto. If the object is brighter, then it is likely smaller, while a darker object would be larger. Similar objects could have helped to build the dwarf planet in the past.

"There's so much that we can learn from close-up spacecraft observations that we'll never learn from Earth, as the Pluto flyby demonstrated so spectacularly," New Horizons science team member John Spencer, also of SwRI, said in the statement. 

"The detailed images and other data that New Horizons could obtain from a KBO flyby will revolutionize our understanding of the Kuiper Belt and KBOs."

 There's so much that we can learn from close-up spacecraft observations that we'll never learn from Earth, as the Pluto flyby demonstrated so spectacularly," New Horizons science team member John Spencer, also of SwRI, said in the statement. 

"The detailed images and other data that New Horizons could obtain from a KBO flyby will revolutionize our understanding of the Kuiper Belt and KBOs."